1. Field of the Invention
This invention relates to well tools and more particularly to the treating of subterranean formations in wells by processes known as acidizing, gravel packing, formation fracturing, and the like processes, for sand control and/or increased production, such as of hydrocarbons.
2. Description of the Prior Art
It has been known to treat wells, such as oil or gas wells, with treating media, such as acids, plastics, cements, sand or gravel-laden liquids, and the like fluids, for the purpose of controlling sand, paraffin, or the like, or for increasing productivity of the producing formations, et cetera. It is common to perform a plurality of such operations in sequence. For instance, it is common to treat a well with acid (to acidize) before performing a gravel packing operation, or before performing a sand fracturing and propping operation. Further, it is common to perform a plurality of operations in sequence, wherein one or a plurality of liquids is forced into the producing formation. Furthermore, it is common practice to remove excess treating fluids from a well immediately after such individual operations. Oftentimes, it is necessary to disconnect the pipe string from the packer in order to remove such excess treating fluids. (This removal is generally accomplished by reverse circulation, as opposed to conventional circulation.) After the pipe string has been disconnected from the packer, it has not been practical to reconnect it again for performing additional treating operations, since there was a great risk that seals or equipment downhole would be damaged and their functioning made questionable, and there was a risk that pressures would lift the apparatus out of position during the treatment. Consequently, it has been common practice to withdraw the pipe string, redress the equipment, and rerun it into the well. Also, in lifting the pipe string relative to the packer in order to reverse circulate to effect removal of excess treating fluids, seals normally engaged in the packer bore are disturbed, or moved a long ways out of place, or are completely removed from the packer, thus exposing the internal wall of the packer to hostile agents such as acids which might damage this inner wall to such extent that seals will no longer sealingly engage therein, or be roughened to such extent that the seals will be abraded and ruined as they are forced into place in the packer bore.
The present invention is embodied in equipment which permits sequential operations to be carried out in a well by treating the well with a plurality of treating media and reverse circulating cleanout fluids after each phase of treatment without disconnecting the pipe string from the packer and without moving the seals in the packer bore.
Known prior art which relates to this present invention includes the following U.S. Pat. Nos.: 3,398,795 3,710,862 3,893,512 4,180,132 4,321,965.
U.S. Pat. No. 3,398,795 which issued to Thomas L. Elliston for RETRIEVABLE WELL PACKERS on Aug. 27, 1968, teaches use of a retrievable well packer having slips for locking the packer in the well casing against displacement therein in either longitudinal direction, this packer being typical of packers adaptable for use in practicing the present invention.
U.S. Pat. No. 3,710,862 issued on Jan. 16, 1973 to Carter R. Young, et al, for METHOD AND APPARATUS FOR TREATING AND PREPARING WELLS FOR PRODUCTION. The present invention is an improvement over the methods and apparatus taught in this patent.
U.S. Pat. No. 3,893,512 which issued July 8, 1975 to Albert W. Carroll, et al, for METHOD AND APPARATUS FOR CONTROLLING FLOW FROM WELLS, shows a telescoping joint used downhole in a pipe string to provide limited relative longitudinal movement.
U.S. Pat. No. 4,180,132 issued Dec. 25, 1979 to Carter R. Young for SERVICE SEAL UNIT FOR WELL PACKER. The present invention is an improvement over the service seal unit tool disclosed in this patent.
None of the prior art of which applicants are aware shows apparatus for performing treating operations such as acidizing, gravel packing, or the like operation in a well wherein the excess treating medium is removed via reverse circulation of cleanout fluids without disconnecting the pipe string from the packer and without substantially moving the seals in or from the packer bore during the treating operation.